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By Roger Highfield on

Boost life expectancy with a plant-based diet

A systematic review and analysis have shown plant-based diets are healthy, complementing research that shows they benefit the planet too. Roger Highfield, Science Director, reports on today’s study.

Swapping red or processed meat and eggs for legumes, nuts and whole grains is associated with reduced risk of death and health conditions such as cardiovascular disease and type 2 diabetes, concludes the first systematic review of the health impact of the substitution of animal-based foods with plant-based foods.

One earlier study concluded, for example, that a young American adult could add more than a decade to their life expectancy by changing their diet from a typical Western diet to one with more legumes, whole grains and nuts, and less red and processed meat. Another, published last month, concluded that eating more than one weekly serving of red meat may raise type 2 diabetes risk.

Vegetables at Borough Market, Southwark Street, London. Photo by Ian Ward on Unsplash.

Following up growing evidence of the benefits to health and to the environment of the substitution,  the study, published today in BMC Medicine, was to meet the ‘urgent need’ for a systematic review of the overall health impact of substitution.

After trawling through more than one thousand relevant studies, the team summarised findings from 37 publications, including 24 studies of the associations between substituting animal-based foods (including red and process meat, poultry, fish and shellfish, eggs, and dairy) for plant-based foods (including legumes, nuts, whole and refined grains, fruit and vegetables, and oils) and health.

The health impacts were weighed up by Sabrina Schlesinger of the German Diabetes Center in Düsseldorf, Lukas Schwingshackl of the University of Freiburg and colleagues and covered cardiovascular diseases such as coronary heart disease, heart attack, and stroke incidence, type 2 diabetes incidence and mortality, along with all-cause mortality.

The relative risk of cardiovascular disease was reduced by 27 percent when 50 grams of processed meat per day was swapped with between 28 and 50 grams of nuts while the relative risk was decreased by 23 per cent if the processed meat was substituted by 50 grams of legumes. In comparison to nuts, ‘legumes are also nutritionally rich, containing fibre, protein, vitamins, and minerals, but they might have different bioactive compounds and nutrient profiles than nuts,’ comments Schlesinger.

Replacing one egg per day with between 25 and 28 grams of nuts was associated with a 17 percent reduced risk.

When it comes to processed meat, for example, one explanation is that it contains saturated fatty acids, such as stearic and palmitic acid, which potentially increase the risk of cardiovascular disease and diabetes, along with compounds promoting oxidative stress and chronic low-grade inflammation.

In contrast, plant-based foods such as nuts, legumes, and whole grains, as well as olive oil, contain high amounts of antioxidant and anti-inflammatory compounds, including fibre, phytochemicals, vitamins and minerals, and polyphenols that show beneficial associations with cardiovascular health and obesity, and can lower blood pressure.

However, there was no clear evidence that replacing poultry and fish or seafood with nuts or legumes reduced the risk of cardiovascular disease.

When it came to the incidence of type 2 diabetes, swapping 50 grams per day of processed meat for between 10 and 28 grams of nuts was associated with a 22 percent reduced relative risk, and replacing one egg per day with 30 grams of whole grains or 10 grams of nuts was associated with a 21 percent and 18 percent decreased relative risk, respectively.

Additionally, replacing 50 grams per day of processed meat with 28 to 50 grams of nuts was associated with a 21 percent relative risk reduction in all-cause mortality.

There were also some more specific findings: ‘our meta-analysis demonstrates a decrease in the relative risk of cardiovascular disease, type 2 diabetes, and all-cause mortality when butter is replaced with olive oil,’ says Schlesinger.

There were also associations with a lower risk of all-cause mortality when substituting animal cooking oil with plant oils other than peanut, soybean, canola, or salad oil.

‘Interestingly, our findings indicated that it’s not just the replacement of red and processed meats with whole grains, nuts, and legumes that showed associations with cardiometabolic health and all-cause mortality. It also points out that substituting other animal-based foods, such as poultry and eggs with these plant-based foods demonstrated similar association (especially for type-2-diabetes),’ says Schlesinger.

Though they conclude that a change in dietary habits away from meat towards plant-based products appears to be important for health, more research is necessary, notably when it comes to inconsistent findings on replacing processed and unprocessed meat, on the health impact of meat and dairy substitutes and to weigh up the impact over longer periods.

Adapting to a plant-based diet has dual benefits: improved health outcomes and a reduced environmental impact. ‘This study is significant in confirming that the scientific evidence shows that as well as climate benefits there are clear health benefits to eating less meat and more plant-based whole foods, like legumes, nuts and vegetables, in Western diets,’ commented curator Rupert Cole, who is working on an exhibition about the future of food.